DOCUMENT:Q280447  07-MAY-2002  [visualc]
TITLE   :BUG: Text from a Rich Edit Control Is Truncated During DDX
PRODUCT :Microsoft C Compiler
PROD/VER::6.0
OPER/SYS:
KEYWORDS:kbCmnCtrls kbMFC kbRichEdit kbClassWizard

======================================================================
-------------------------------------------------------------------------------
The information in this article applies to:

 - Microsoft Visual C++, 32-bit Editions, version 6.0 
-------------------------------------------------------------------------------

SYMPTOMS
========

The text in a rich edit control may be truncated under the following
circumstances:

 - You associate a CString variable with the rich edit control on a dialog box
   template.

 - The rich edit control exceeds 64 kilobytes (KB).

CAUSE
=====

This problem occurs because the WM_GETTEXT message is not programmed to work
with rich edit controls that are larger than 64 KB. The Class Wizard generates
code that uses the DDX_Text function to exchange data between the rich edit
control and the CString variable. The DDX_Text function uses the GetWindowText
function, which sends the WM_GETTEXT message to the control to retrieve the text
in the control. The WM_GETTEXT message does not accept text that is larger than
64 KB.

RESOLUTION
==========

To work around this problem, use the DDX_RichText function as demonstrated in
the "More Information" section of this article.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article.

MORE INFORMATION
================

To work around this problem, add the following two functions to your project:

       DWORD CALLBACK ES2MemCallBack(DWORD_PTR dwCookie,
                                     LPBYTE pbBuff, LONG cb, LONG *pcb)
       {
           LPTSTR& lpszStrFill = *(LPTSTR*)dwCookie;
           memcpy(lpszStrFill, pbBuff, *pcb = cb);
           lpszStrFill += cb;
           *lpszStrFill = TCHAR('\0');

           return 0;
       }

       void AFXAPI DDX_RichText(CDataExchange* pDX, int nIDC, CString& value)
       {
           extern void AFXAPI AfxSetWindowText(HWND hWndCtrl, LPCTSTR lpszNew);
           HWND hWndCtrl = pDX->PrepareEditCtrl(nIDC);
           if (pDX->m_bSaveAndValidate)
           {
               int nLen = ::GetWindowTextLength(hWndCtrl);

               LPTSTR lpszStrFill = value.GetBufferSetLength(nLen);
               EDITSTREAM es = { (DWORD_PTR) &lpszStrFill, 0, ES2MemCallBack };
               ::SendMessage(hWndCtrl, EM_STREAMOUT, SF_TEXT, (LPARAM) &es);
               value.ReleaseBuffer();
           }
           else
           {
               AfxSetWindowText(hWndCtrl, value);
           }
       }

To add Class Wizard support for the new data exchange function, add the following
lines to the .clw file or to the Ddx.clw file of your project:

See the "References" section of this article for more information about DDX and
DDV Routines.

       ExtraDDXCount=1
       ExtraDDX1=7;;TextOver64KB;CString;;RichText;Retrieves text in excess of 64KB from RichEdit controls

Alternatively, if the ExtraDDXCount line already exists, you can increment the
value of ExtraDDXCount by one.

NOTE: Seven is the numeric constant that indicates a rich edit control.

If you do not use the preceding step, you must manually replace all calls to
DDX_Text with DDX_RichText. Then, you must move these calls outside the
wizard-controlled code. Wizard-controlled code is the code that is bracketed by
//{{AFX_DATA_INIT(...) and //}}AFX_DATA_INIT, and //{{AFX_DATA_MAP(...)
//}}AFX_DATA_MAP.

For more information about DDX and dialog data validation (DDV) routines, see the
"References" section.

REFERENCES
==========

For more information, see the following MSDN Web sites:

TN026: DDX and DDV Routines:
http://msdn.microsoft.com/library/devprods/vs6/visualc/vcmfc/_mfcnotes_tn026.htm

Windows User Interface WM_GETTEXT:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/windows_34ok.asp

Additional query words: CRichEdit truncate

======================================================================
Keywords          : kbCmnCtrls kbMFC kbRichEdit kbClassWizard 
Technology        : kbVCsearch kbAudDeveloper kbVC600 kbVC32bitSearch
Version           : :6.0
Issue type        : kbbug
Solution Type     : kbpending

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS
PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND.  MICROSOFT DISCLAIMS
ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  IN NO
EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR
ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL,
CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF
MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES.  SOME STATES DO NOT ALLOW THE EXCLUSION
OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES
SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 2002.